1. Technical Field of the Invention
This invention pertains to inter-operability among various computer platform architectures existing in a network. More particularly, it pertains to providing the look and feel of character interactive I/O operation across separate architectures.
2. Background Art
In a client/server computer network, inter-operability among the various platform architectures that exist in the network is a primary goal of the network. In particular, client/server network applications such as Telnet, SMTP, FTP, LPD, etc. are expected to be able to work equivalently, independent of the platform architecture on which they are implemented. However, due to differing architectures of the various platforms, there are often obstacles that severely limit developing and providing a common “look and feel” in terms of network application user interfaces presented on each platform.
One such architecture example is the half-duplex block-mode display devices supported by the IBM 5250 architecture iSeries (AS/400) and 3270 (S/390) platforms. Another architecture example is the character interactive I/O architecture, such as supported by UNIX (including AIX, Linux, etc.)
There is a need in the art for a system and method for providing the same “look and feel” of network applications on each platform, even though they must be supported differently by the architectures. The physical rendering of the client user interface can often limit the logical requirement of the server application in the network.
For example, when using Telnet from a UNIX platform to communicate with an iSeries platform, it is expected that using Telnet from the iSeries platform to the UNIX platform (the reverse direction) will work in an equivalent manner and have similar “look and feel” at the user interface. Failure to work in such a bi-directional manner is an inter-operability problem. Failure to inter-operate creates significant user dissatisfaction due either to loss of functionality or the need to learn custom circumventions or work arounds. Worse, lack of inter-operability leads to inability to market or sell a product as a solution in a client/server computer network.
One such networking inter-operability problem exists between the iSeries and the UNIX platforms. The iSeries is a half-duplex block-mode display device architecture, which is characteristic of all 5250 and 3270 based display devices and any clone implementation. The UNIX box is a character interactive echo-plexed architecture. UNIX based display sessions are based on VTxxx type terminals and define a standard character interactive I/O keyboard as the default that must be supported by any display clients wishing to run traditional text display based UNIX applications. In the Telnet protocol, a client host rendering a display should emulate the VTxxx (i.e. VT100, VT220) based display and keyboard characteristics to the best of its ability. Due to the IBM 5250/3270 display device architecture of half-duplex block-mode buffering, generally characters are collected in a buffer until an action identifier (AID) key is entered (such as Enter, program function PF1–PF24 keystrokes, etc.) and all the keystrokes in the buffer transferred to the iSeries application, rather than processed one at a time by an application. This conflicts with the need for a VTxxx type terminal to do character interactive I/O, which essentially means it needs to process each character as it is typed. This means each character keystroke typed in a half duplex block mode (iSeries Telnet) client session that is running a character interactive I/O application on a UNIX server does not necessarily get processed within the context of the server application as a VTxxx keystroke. Instead, it is buffered in the iSeries display device until an action keystroke is pressed. The action keystroke required is normally an enter or program function (PF) key. This is a character interactive I/O inter-operability problem on the Telnet client side.
An example of a character interactive I/O inter-operability problem involves password fields. In a native character interactive ASCII environment when the client connects to a UNIX Telnet server, the user is presented with a login (or sign-on) panel in which to enter the profile or userid name and password. Typically, each character of the profile or userid name is echoed to the screen as it is typed in, and the cursor position moves with each character typed in. However, each character of the password is hidden by the application itself, which echos a replacement character or characters, such as an asterisk “*”, blanks, XXXX, etc. . . , or by not echoing a character at all and leaving the cursor position unchanged. Unfortunately, again due to half-duplex block-mode architecture design, character substitution does not automatically occur for an iSeries Telnet client or other similarly architected clients operating in half duplex mode. The current iSeries Telnet client circumvention requires the user to press the program function key assigned to the special function “hide keystroke echoes until the next action key”, which is set to PF6 by default for iSeries Telnet client. This local “hotkey function” signals the iSeries Telnet client program that the characters that follow are to be hidden. The iSeries Telnet client refreshes the screen input fields with non display attributes therein instructing the display device to simply send in the keystrokes with the next action key (AID) to avoid displaying the keystrokes to the screen. This also has the side effect of defeating the ability of the application to substitute any preferred different “echo” characters, such as echoing a “XXXX”, or “**” or “??” string for each character typed (something Lotus Notes does). Again, this solution is rather awkward from a customer perspective, requires knowledge of the circumvention and is not intuitive.
Another example of a character interactive I/O inter-operability problem relates to the use of graphical characters in different contexts. Consider a Lotus 1-2-3 spreadsheet application to work with saved 1-2-3 files. Lotus 1-2-3 has a classic menu hotkey, where the spreadsheet application recognizes the “/” as a special version of the introducer character. In the context of the Lotus 1-2-3 application, the “/” character is to be used as a command to pop up an application selection menu, not as a direct character to be echoed to the display or typed into the spreadsheet itself. In order to send the “/” alone as a real ASCII client would, the iSeries has to use the PF11 (“send without carriage return”) trick to cause a client Telnet to avoid sending the Enter keystroke equivalent for ASCII carriage return (0x0D).
These examples are deviations from VTxxx defacto standards required by users of 5250/3270 architectures, and it forces users to memorize custom circumventions that are generally not well-known to the average character interactive I/O network user. These circumventions are not well received by customers when 5250/3270 platforms are marketed as a solution in any network with character interactive I/O operating systems, and ironically do not inter-operate with Linux, or AIX (a RISC platform).